GSAS-II is an open source Python project that addresses all types of crystallographic studies, from simple materials through macromolecules, using both powder and single-crystal diffraction and with both x-ray and neutron probes. Measurements can be constant wavelength (or in the future, neutron TOF.) At present, code is being developed for all the various steps in diffraction analysis, such as data reduction, peak analysis, indexing, structure solution and structure refinement.
see: http://onlinelibrary.wiley.com/doi/10.1107/S0021889813003531/abstract